Optimizing the FDFD Method in Order to Minimize PML-Related Numerical Problems

Using the PML boundary condition in the finite-difference frequency-domain (FDFD) method can significantly affect the numerical condition of the resulting system of equations, causing a drastic increase in the CPU time. This paper presents in-depth investigations of the underlying effects as well as measures to improve numerical convergence. The results are verified for various microwave structures such as a flip-chip interconnect, a multi-layer transition, and a patch antenna. They apply not only to the FDFD method but similarly to other frequency-domain as well as time-domain approaches.